Mechanical keying

Mechanical key system This provides a basic level of security for heavily used areas. Although complicated mechanisms can be designed, their operation is slow, and hence is suitable only for limited access. 

Principles The process consists of tumbling the metal to be coated with a powder of the coating metal. It is considered that a form of welding is involved, but the type of conditions conducive to successful deposition indicates that the deposit adheres by mechanical keying (A/, must therefore be relatively soft) and adhesive forces. Thus pretreatments such as abrading or pickling enhance the keying effect, and the use of a soft metal... 

Vandanme, L., Jeffrey, R.G. and Curran, J.H. "Effects of Three-Dimensionalization on a Hydraulic Fracture Pressure Profile," 1986 Proc. U.S. Sumposium on Rock Mechanics Key to Energy Production 580-590, Tuscaloosa, Alabama, June 23-25. 

Figure 7. Polar plots of the reaction product vector for three surface mechanisms. Key a, simple adsorption-desorption b, series process, kt = kd = k and c, branch...

Figure I. Oxyphosphorane intermediates corresponding to possible primary reaction pathways (I)-(4) in hydrolysis of[y-M0] A TP in lN and 0.1 N HCl by the addition-elimination mechanism. Key 1 denotes attack by water on Pg 2 and 3, on Pp 4, on Pa denotes the heavy isotope, sO.

Figure 5. Calculated volatile flux from 1.5 cm pellet vs. time for complex reaction mechanism. Key ------------------, total volatiles -, tar and-, gas.

The Fischer esterification mechanism (Key Mechanism 20-2) is an acid-catalyzed nucleophilic acyl substitution. The carbonyl group of a carboxylic acid is not sufficiently electrophilic to be attacked by an alcohol. The acid catalyst protonates the carbonyl group and activates it toward nucleophilic attack. Attack by the alcohol, followed by loss of a proton, gives the hydrate of an ester. 

Peg is produced by the selective oxidation of the RE at the scale alloy interface causing mechanical keying of scale... 

The most important aspect of pre-treatment is to provide the optimum surface roughness to give mechanical "keying" of the film to the surface. It is generally accepted that the optimum surface finish is between 0.5 and 2.0//m c.I.a. Most of the published work on surface finish effects has been related to bonded films, and the subject is described in detail in Chapter 11, but similar surface finishes are also desirable for burnished films, especially on hard substrates. However, for sputtered films, which may be only 1//m thick, much smoother substrate surfaces give the maximum life. 

Structure and Mechanism Key Experimental Methodology Energetics of the Pump... 

X-ray crystallography is a powerful and direct tool to understand kinase inhibitory mechanisms. Key experiments demonstrate that inhibitors interact with multiple regions of kinases that lead to mechanisms that may or may not be competitive with substrates. As examples, p38 inhibitors fall into both groups. 

Figure 1. Idealized plots relating molecular weight ratio to depolymerization mechanisms. Key A, end-group depolymerizationfollowed by complete unzipping B, random scission followed by complete unzipping C, end-group depolymerization followed by incomplete unzipping and D, random depolymerization followed by incomplete...

Assembly processes are monitored by means of integrated control devices (mechanical keys, inductive feeders, etc.) in the assembly stations or partly in separate stations. This is a very important function from a quality-assurance point of view. For short-cycle assembly machines, either force-moved or pneumatic-driven motion facilities are used in the assembly stations. 

Figure 5 Adhesion of copper to silica using a mechanical key (a)-(d) successive stages (see text) (after Ref. 66).

The adherend, adhesive, and interphase between them are major faetors in determining bond durability. For example, the simple disruption of the dispersive forees already described indicates that joints made with eomposite adherends will be inherently more stable than those made with metallie adherends. To inerease durability, most metallie and many polymeric adherends undergo surfaee treatments designed to alter the surfaee ehem-istry or morphology to promote primary eovalent ehemieal bonds and/or physieal bonds (mechanical keying or interlocking) to maximize, supplement, or replaee seeondary dispersive bonds. These treatments are diseussed elsewhere [1,3,12,18 24]. An intent of eaeh treatment is to provide interfacial bonding that is resistant to moisture intrusion. 

The provision of an improved mechanical key. In cementitious repair work the bond coat , while still tacky, may be dry-dashed with sharp sand. 

Garnish and Haskins found that exposure of polypropylene to trichloroethylene vapour for 10 s resulted in a sixfold increase in joint strength using an Epoxide adhesives. The authors concluded that the improved adhesion was due to the removal of a weak boundary layer. However, the treatment causes the formation of a very porous surface, and an alternative explanation for the improved adhesion is the mechanical keying of the adhesive into the porous surface (see Mechanical theory of adhesion). Garnish and Haskins found that the optimum treatment time was about 10 s and that after 25 s the adhesion level was similar to that of the untreated polymer. This reduction is probably due to weakening of the surface region of the polypropylene. 

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